UV-Vis Analysis of Au-HRP Solutions

The Au-HRP solutions were made on 2012/11/07 and the spectra of the solutions were obtained over 200 to 800 nm in quartz cuvettes. Please refer to Dhea Patel's entry for a photograph of the solutions.

Peaks at around 300 and 520 nm were visible. The peak at 520 nm indicates the presence of GNPs in the 50, 100, and 150 mole ratio Au:HRP solutions.

The peak at around 300 nm was present in the spectra of the 250, 300, 350, 400, and 450 mole ratio Au:HRP solutions. It is possible that this peak is due to the relatively higher concentration of HAuCl4 in these solutions, based on literature. Note that the literature indicated that a peak at around 287 nm is present in the spectra of aqueous HAuCl4.

Gold was detected in solutions at mole ratios of Au-lys from 20 to 60. The 60 Au-lys solution had the highest concentration of gold. This agrees with UV-vis data obtained on 2012/11/06. However, no peak or a slight peak was visible on the spectrum of the 20 Au-lys solution. This is corroborated by the fact that the AAS detected that the solution contained 0.0057 ppm Au.

The 70 through 130 AuLys solutions displayed the highest percent change in [Au], likely because the GNPs were aggregated with the lysozyme fibers. The 20 AuLys solution displayed the second highest percent change [Au] probably due to a procedural error. The detection limit of the AAS is between 2 and 4 ppm Au, and the amount of Au initially added to this solution was around 3 ppm. Therefore, it can be hypothesized that the AAS was unable to detect the actual [Au] in this solution.

It can be assumed that the fibers formed in the rest of the Au-lys solutions at mole ratios from 70 to 130 encapsulated the gold, such that there was no free gold or gold nanoparticles in solution. Theoretically, the gold concentration in these solutions was zero, but the AAS registered negative concentrations due to the fact that it was blanked with 1 N HCl, as opposed to deionized water.

Mole Ratio of Au to HRP

Au [ppm]

10

-1.5443

50

1.8191

100

11.7714

150

13.1419

200

23.6748

250

24.4588

300

27.876

350

25.4761

400

35.1173

450

25.6198

HRP []

HAuCl4 []

HRP [uL]

HAuCl4 [uL]

Water [uL]

Mol Au [mol]

Mass Au [mg]

Initial [Au] [ppm]

Final [Au] [ppm]

Change in [Au] [ppm]

Percent Change in [Au] [%]

1

10

280.7

7.62

7711.7

0.00000008

0.01575736

1.96967

-1.5443

3.51397

178.4039966

1

50

280.7

38.1

7681.2

0.0000004

0.0787868

9.84835

1.8191

8.02925

81.52888555

1

100

280.7

76.2

7643.1

0.0000008

0.1575736

19.6967

11.7714

7.9253

40.23668939

1

150

280.7

114.3

7605.0

0.0000012

0.2363604

29.54505

13.1419

16.40315

55.51911403

1

200

280.7

152.4

7566.9

0.0000016

0.3151472

39.3934

23.6748

15.7186

39.90160788

1

250

280.7

190.5

7528.8

0.000002

0.393934

49.24175

24.4588

24.78295

50.32914143

1

300

280.7

228.5

7490.7

0.0000024

0.4727208

59.0901

27.876

31.2141

52.82458483

1

350

280.7

266.6

7452.7

0.0000028

0.5515076

68.93845

25.4761

43.46235

63.04515115

1

400

280.7

304.7

7414.6

0.0000032

0.6302944

78.7868

35.1173

43.6695

55.42743201

1

450

280.7

342.8

7376.5

0.0000036

0.7090812

88.63515

25.6198

63.01535

71.09521448

The concentration of Au in ppm increased as the mole ratio of Au:HRP increased. However, there was the greatest percent change in [Au] in ppm in the 10 AuHRP solution. However, as the limit of detection of the AAS for Au is around 2-4 ppm Au, the AAS was likely unable to accurately detect the actual concentration of Au in this solution. The lowest percent change in Au ppm was observed for the 200 AuHRP solution, so it is likely that this mole ratio is the best at producing GNPs relative to the amount of Au added before the reaction between Au and HRP.